Venetian blind having prismatic reflective slats

ABSTRACT

A venetian blind having prismatic reflective slatted panels permits the passage of indirect rays of sunlight into a space to be illuminated while reflecting direct rays of sunlight away from the space to be illuminated. The prismatic reflective slats are supported for rotation in unison to follow elevational movements of the sun. Each of the prismatic panels is made from a light transmissive material having a front face directed at the sun and an opposing rear face upon which reflective prisms are formed for internally reflecting rays of sunlight that strike the front face of each slatted panel at approximately a 30° angle from a line normal to the front face thereof. The orientation of the reflecting prisms in this manner maximizes overall visibility between adjacent slatted panels. A diffusion panel is secured to the rear face of each prismatic reflective slat for diffusing indirect rays of sunlight transmitted through the prismatic reflective slats. The prisms formed upon the rear face of each reflective slat may be linear prisms or triangular pyramidal prisms.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to shading mechanisms used tocontrol the passage of sunlight into a space to be illuminated, and moreparticularly, to a venetian blind structure incorporatinglight-transmissive prismatic slatted panels for reflecting glaringdirect rays of sunlight while transmitting indirect rays of sunlight.

2. Description of the Prior Art

Many types of curtains, blinds and screens are known for controlling theamount of natural daylight admitted into a room or building through awindow, skylight, or other light opening. In most cases, such curtains,blinds or screens are totally or partially opaque to shade the area tobe illuminated from direct glaring rays of sunlight. However, the opaqueportions of such light control devices also block indirect rays ofsunlight which strike such opaque portions from reaching the area to beilluminated. In addition, such opaque light control devices absorb heatfrom blocked rays of direct sunlight, and may thereby add undesired heatto the area being illuminated.

Light control mechanisms have also been disclosed wherein transparentlenses, slats, or blinds are used to selectively admit or reflect raysof sunlight. For example, U.S. Pat. No. 3,438,699 discloses a multipleslat assembly similar to a venetian blind wherein each slat is composedof two transparent pieces of material having interfitting prisms toexclude light and heat rays coming from a particular direction. U.S.Pat. Nos. 2,812,690; 2,812,691; 2,858,734; and 2,993,409 all discloseskylights having prismatic lenses for selectively admitting orreflecting rays of sunlight. U.S. Pat. No. 2,812,692 discloses a glassblock structure using prismatic surfaces to selectively admit or reflectrays of sunlight depending upon their angle of entry. U.S. Pat. No.3,393,034 discloses a light control blind using a series of elongatedrectangular panels, each panel being formed of intermeshing pairs ofprismatic plates for blocking downwardly directed light rays whilepermitting the passage of upwardly directed light rays. U.S. Pat. No.4,517,960 also discloses a slatted structure wherein light-permeableslats have a prismatic surface for reflecting direct overhead rays ofsun.

Apart from blocking direct rays of sunlight from passing into theilluminated space, it is also an objective of many light control blindsto permit a person within the illuminated area to be able to lookthrough the blind in order to view the outdoors. Some prior art devicesachieve this objective by intermeshing a second prismatic panel with thefirst prismatic panel, so that light rays refracted away from theiroriginal angular path by the first prismatic panel are refracted back totheir original angular path by the second prismatic panel. However, suchstructures often exhibit alternating clear and dark bands which aredistracting and which interfere with a clear view through the blindstructure. Moreover, the blind structures shown in U.S. Pat. Nos.3,438,699 and 4,517,960 use linear prisms which are formed symmetricallyabout the light entry face of each slat; accordingly, the slats of eachsuch blind structure would need to be set at approximately a 45° anglein order to ideally reflect direct rays of sunlight approaching from a45° angle of elevation from the horizon. However, positioning the slatsat a 45° angle would virtually eliminate any level line of sight betweenadjacent slats. Furthermore, while such prior art blind structures maypermit limited viewing of the outdoors through the slat elementsthemselves, any attempt to incorporate a diffusion element to moreevenly diffuse the light transmitted by such slats would interfere withthe ability to view the outdoors through the slats of the blind.

Accordingly, it is an object of the present invention to provide a shademechanism which permits the passage of indirect rays of sunlight into aspace to be illuminated while substantially reflecting direct rays ofsunlight away from the space to be illuminated.

It is another object of the present invention to provide such a shademechanism which minimizes any interference with vision through the shademechanism for a person located within the illuminated space attemptingto view the outdoors.

It is still another object of the present invention to provide such ashade mechanism using a plurality of transparent, prismatic slattedpanels adapted to reflect direct rays of sunlight, which slatted panelsare normally oriented in a position which permits level vision betweenadjacent slatted panels.

It is yet another object of the present invention to provide such ashade mechanism wherein light transmitted through such slatted panelsmay be diffused to more evenly illuminate the illuminated space withoutinterfering with vision through the shade mechanism.

It is a further object of the present invention to provide such a shademechanism which minimizes heat gain from direct rays of sunlight.

It is a still further object of the present invention to provide such ashade mechanism which may be used on vertical light openings, such asconventional windows, as well as in conjunction with horizontal orslanted light openings.

These and other objects of the present invention will become moreapparent to those skilled in the art as the description thereofproceeds.

SUMMARY OF THE INVENTION

Briefly described, and in accordance with a preferred embodimentthereof, the present invention relates to a shade mechanism forpermitting the passage of indirect rays of sunlight into a space to beilluminated while reflecting direct rays of sunlight away from the spaceto be illuminated, the shade mechanism including multiple slattedpanels, each supported for rotation about its longitudinal axis. Theslatted panels are supported in venetian blind fashion, and a tiltmechanism is provided for causing each of the slatted panels to rotatein unison, while maintaining the multiple slatted panels parallel to oneanother. Each of the multiple slatted panels is made of a substantiallyclear, light transmissive material. Each such panel has a front face forbeing directed at the sun and an opposing rear face having prisms formedthereon. The prisms formed upon the rear face of each such panel causerays of sunlight striking the front face of each such panel within apredetermined band of angles to be internally reflected and emitted backout through the front face of each such panel. The prisms formed uponthe rear face of each such panel permit indirect rays of sunlight lyingoutside the aforementioned angular range to be transmitted through suchpanel into the space to be illuminated.

In order to minimize interference with vision between adjacent panels,the prisms formed upon the rear face of each such panel are adapted tofocus upon and internally reflect direct rays of sunlight which strikethe front face of each such panel in a predetermined band of anglesextending substantially symmetrically about a central focal angle. Thecentral focal angle lies within the range of about 20°-40° to thenormal, relative to the front face of each such slated panel.Preferably, the central focal angle lies within the range of 25°-35° tothe normal, and in the preferred embodiment, the central focal anglelies at substantially 30° to the normal relative to the front face ofeach such slatted panel, in order to maximize visibility between theslatted panels under normal operating conditions. Preferably, the tiltmechanism is adapted to position the multiple slatted prismatic panelsin a manner such that a plane lying parallel to the longitudinal axis ofa slatted panel and containing a direct ray of sunlight will interceptthe front face of each such panel at an angle of approximately 30° tothe normal in order to maximize reflection of direct rays of sunlight.Accordingly, the tilt mechanism ideally includes a solar trackersensitive to the position of the sun for controlling rotation of theslatted panels in response to daily and seasonal movements of the sun.If desired, an offset may be incorporated into the solar tracker duringwinter months to transmit direct rays of sunlight when additionalheating is required.

In its preferred form, the present invention further includes adiffusion panel associated with each slatted panel and positionedadjacent the rear face of each slatted panel for diffusing lighttransmitted through each such slatted panel. Such diffusion panelsfunction to disperse any errant rays of direct sunlight that are notreflected by the prismatic slatted panels; in addition, diffusion panelsserve to diffuse the transmitted indirect rays of sunlight to moreevenly illuminate the room. During winter months, such diffusion panelsdisperse direct rays transmitted through the slatted panels. Suchdiffusion panels may be made of a translucent material or a transparentmaterial having an irregular surface. An insulating air space may becreated between the rear face of each slatted panel and its associateddiffusion panel for increasing the insulative properties of the shademechanism when the slats are fully closed. The diffusion panels may betinted to impart colorization to the transmitted light.

The prisms formed upon the rear face of each slatted panel may be of anytype which is adapted to internally reflect direct rays of sunlightapproaching from within the range of angles of light to be rejected.Preferred forms of prismatic surfaces include pyramidal prisms (such asmultifaceted pyramidal prisms, conical prisms, and semi-sphericalprisms) and linear elongated prisms.

Slatted panels using linear elongated prisms may be formed by providinga series of 3-faced linear prisms upon the rear face of each slattedpanel. Each 3-faced linear prism preferably has first and second facesof approximately equal width disposed at a right angle to one another,and including a third face extending between successive pairs of suchfirst and second faces. The first and second faces of each 3-facedlinear prism are oriented so that a plane bisecting the angle formedbetween the first and second faces extends parallel with refracteddirect rays of sunlight as they pass from the front face to the rearface within each slatted panel.

As set forth above, the first and second faces of each 3-faced linearprism focus upon and reflect direct rays of sunlight striking the frontface of each such slatted panel in a predetermined band of angles thatextends symmetrically about a central focal angle. The central focalangle for incident direct rays of sunlight lies within the range of20°-40° to the normal relative to the front face of the panel, andpreferably within the range of 25°-35°, with the central focal angle of30° to the normal, relative to the front face of the panel, being thepreferred orientation. For light-transmissive materials exhibiting anindex of refraction of approximately 1.5, rays of direct sunlightstriking the front face of the slatted panels at an incident angle of30° to the normal will be refracted at an angle of approximately 20° tothe normal; accordingly, the first and second faces of each 3-facedlinear prism are preferably oriented so that a plane bisecting the angleformed therebetween lies at 20° to the normal. The third face of each3-faced linear prism is also preferably set at 20° to the normal toavoid interference with the reflection of direct rays of sunlight by thefirst and second faces.

Each slatted panel may, if desired be formed as a curved or segmentedstructure rather than as a planar structure. In such event, each 3-facedlinear prism is oriented to internally reflect direct rays that strikethat portion of the front face of the slatted panel lying proximate eachsuch 3-faced linear prism.

In one embodiment of the present invention, the front face of eachslatted panel has a stepped surface consisting of alternating first andsecond surfaces arranged substantially perpendicular to one another.Each of the first surfaces is disposed at an angle of approximately 30°from the front face of the slatted panel as a whole in order to presenta surface that is substantially perpendicular to the direct rays ofsunlight that are to be reflected, while the second such surface isoriented parallel thereto. In this case, the path of the direct rays ofsunlight to be reflected by the slatted panel is not initially alteredas the rays of light pass into the slatted panel, and accordingly, thefirst and second faces of the 3-faced linear prisms are oriented suchthat a plane bisecting the angle formed therebetween is perpendicular tothe aforementioned first surface. The number of steps formed upon thefront face of each slatted panel may be equal to the number of 3-facedprisms formed upon the rear face of each such slatted panel.

In an alternate embodiment of the present invention, the rear face ofeach slatted panel includes a series of prismatic surfaces eachextending parallel to the longitudinal axis of the slatted panel andextending generally parallel to one another. A corresponding group ofsecond surfaces are interposed between successive prismatic surfaces.Each prismatic surface is inclined at an angle with respect to the frontface of the slatted panel as a whole, and each prismatic surfaceincludes two or more prisms for reflecting direct rays of sunlight backout through the front face of the slatted panel. Preferably, eachprismatic surface includes a number of consecutive, symmetrical 2-facedlinear prisms having first and second faces angled at 90° to oneanother. In those instances when the front face of the slatted panel isrelatively smooth, a plane bisecting the first and second faces of oneof the 2-faced linear prisms intersects the front face of the slattedpanel at an angle of substantially 20° to the normal so that rays ofdirect sunlight striking the front face at an incident angle of about30° to the normal will be internally reflected by the 2-faced linearprisms.

Alternatively, the front face of the slatted panel may have a steppedsurface consisting of alternating first and second surfaces, the firstsurfaces of the front face being oriented at an angle of approximately30° to the front face of the slatted panel as a whole. In this instance,the prismatic surfaces of the rear face extend virtually parallel withthe first surfaces of the front face, and the plane bisecting the angleformed between the first and second faces of each 2-faced linear prismextends perpendicular to an overlying first surface of the front face ofthe slatted panel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a shade mechanism in the form of avenetian blind having prismatic reflective slats in accordance with theteachings of the present invention.

FIG. 2 is a cross-sectional view of a prismatic reflective slat takenthrough lines 2--2 as shown in FIG. 1, and showing a sun position sensorfor use in controlling the tilt angle of the slatted panels.

FIGS. 3A, 3B and 3C are edge views of a pair of slatted panels withinthe shade mechanism for various angles of incidence of direct rays ofsunlight.

FIG. 4 is a cross-sectional view of the shade mechanism shown in FIG. 1lying adjacent a window and illustrating the manner in which direct raysof sunlight may be reflected while permitting a view of the outdoorsfrom between adjacent slats.

FIG. 5 is a detailed partial sectional view of a slatted panelincorporating a 3-faced linear prism upon the rear face of the slattedpanel.

FIG. 6 is a partial cross-sectional view of a slatted reflective panelhaving a curved front face and a series of 3-faced linear prisms formedupon the rear face thereof.

FIGS. 7A, 7B, 7C and 7D are cross-sectional views of a slatted prismaticpanel having an associated diffusion panel positioned adjacent the rearface of the slatted panel.

FIGS. 8A and 8B are side views of a unitary prismatic panel andassociated diffusion panel hingedly connected to one another.

FIG. 9 is a partial cross-sectional view of a slatted reflective panelincluding 3-faced linear prisms and illustrating an optional extensionmember associated with the third face of a 3-faced linear prism.

FIG. 10 is a modified form of slatted panel wherein the front facethereof is provided with a stepped surface wherein direct rays ofsunlight to be reflected by the slatted panel initially strike a surfaceoriented perpendicular to such direct rays of sunlight.

FIGS. 11A, 11B, 11C and 11D are bottom views of various embodiments ofslatted panels having triangular pyramidal prisms formed upon the rearfaces thereof.

FIG. 12A shows a substantially flat slatted prismatic panel and anassociated flat diffusion panel.

FIG. 12B is a cross-sectional view of a segmented slatted prismaticpanel and an associated flat diffusion panel.

FIG. 12C is a cross-sectional view of a slatted prismatic panel having acentral bend therein and an associated diffusion panel.

FIG. 13 is a cross-sectional view of a slatted prismatic panel having asmooth front face and a stepped rear face wherein each step includes aplurality of 2-faced linear elongated prisms.

FIG. 14 is a cross-sectional view of a slatted prismatic panel similarto that shown in FIG. 13 but wherein the front thereof is provided witha stepped surface.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 1, a shade mechanism incorporating the present invention isdesignated generally by reference numeral 16. Shade mechanism 16includes an upper support bracket 18 and a plurality of slatted panels20, 22 and 24. Also shown in FIG. 1 is a weighted bottom rail, uponwhich a similar slatted panel may optionally rest. As shown in FIG. 1,shade mechanism 16 may be installed within a window box 28 shown indashed outline, like a conventional venetian blind. A pair of ropeladders 30 and 32 extend from upper support bracket 18 to bottom rail26. As in a conventional venetian blind, rope ladders 30 and 32 supportslatted panels 20, 22 and 24 whereby such panels are spaced apart fromone another at regular intervals and extend parallel to one another.Referring briefly to FIG. 2, it will be noted that rope ladder 32includes a first vertical segment 32', a second vertical segment 32",and an interconnecting rope rung 33 interconnected between verticalsegments 32' and 32" for supporting slatted panel 20. While rope laddersare shown in FIG. 1, other support structures may also be used includinga support structure coupled to the opposing ends of each slatted panel.

Rope ladders 30 and 32 are shown in FIG. 1 as having their upper endssuspended over and around tilt pulleys 34 and 36, respectively forallowing slatted panels 20, 22 and 24 to be rotated in unison about eachof their longitudinal axes while maintaining the slatted panelssubstantially parallel to one another. Tilt pulleys 34 and 36 areengaged with a tilt rod 38 connected to a reversible drive motor 40.Drive motor 40 is operated under the control of electronic circuitrymounted upon printed circuit board 42 located within upper supportbracket 18.

Also shown in FIG. 1 is a pull handle 44 for operating a pair of ropes46 and 48, each of which extends through slotted apertures formed withineach slatted panel 20-24, and each of which is attached at its lower endto bottom rail 26. Pull handle 44 may be operated by a user to raise andlower the slatted blind assembly in conventional fashion.

Referring to both FIGS. 1 and 2, a sun position sensor, designatedgenerally by reference numeral 50, is shown as being secured to theoutermost edge of slatted panel 20, i.e., the edge of slatted panel 20which is closest to the window or other light opening through whichsunlight is directed toward shade mechanism 16. Sun position sensor 50may be of the shaded dual photocell type wherein a pair of photocellassemblies 54 and 56 are disposed on opposite sides of a shade 58.Electronic circuitry mounted on printed circuit board 42 is designed tosense any imbalance in the amounts of light detected by photocellassemblies 54 and 56, and upon detecting such an imbalance, operatesdrive motor 40 in the appropriate direction until a balanced conditionis again achieved. As will be explained in greater detail below, sunposition sensor 50 is set at an angle relative to slatted panel 20 suchthat, in the balanced condition, direct rays of sun strike the upperface of slatted panel 20 at approximately a 30° angle relative to a linenormal to the front or upper face of slatted panel 20. While it isusually desired to reflect away direct rays of sunlight to avoidexcessive heat gain, it may be desired to transmit direct rays ofsunlight during the winter to add heat to the illuminated space. In thisevent, sun position sensor 50 can be modified to incorporate an offsetto purposely misalign the focus of the prisms formed upon the slattedpanels and diffused by associated diffusion panels. Sun position sensor50 can be made to provide such an offset by, for example, modifying theangle at which it extends from slatted panel 20. Alternatively, shade 58may be replaced with a wintertime shade (not shown) havingnon-symmetrical sides to create an offset tracking error. Thiswintertime offset is added to maintain the front faces of the slattedpanels in an offset position wherein a direct ray of sunlight strikesone of the slatted panels at an angle, relative to the normal, lyingoutside of the predetermined band of angles of light reflected by theprisms formed upon the face of each slatted panel. Electronic circuitrywhich may be used to operate drive motor 40 in response to sun positionsensor 50 is disclosed, for example, in U.S. Pat. No. 4,429,952, and thedisclosure of such patent is hereby incorporated herein by reference.

It may be recalled that one of the objectives of the present inventionis to reflect direct rays of sunlight away from the space to beilluminated without substantially interferring with vision of a personwithin the illuminated space through the shade mechanism. Referring toFIG. 4, a cross-sectional drawing is shown of shade mechanism 16positioned adjacent a window 60. While FIG. 1 illustrates only threeslatted panels 20-24, it should be clear that the number of slattedpanels selected may be modified to suit the vertical height of theassociated window. Within FIG. 4, direct rays of sunlight are indicatedby the slanted lines bearing arrowheads, one of which has beendesignated by reference numeral 62. Ray 62 is shown as passing throughwindow 60 and striking the front face of slatted panel 64. Slatted panel64 is shown as being positioned at an angle such that ray 62 formsapproximately a 30° angle with an imaginary line, indicated by referencenumeral 66, that is normal to the front face of slatted panel 64.Referring briefly to FIGS. 3A-3C, incident rays of direct sunlight aredesignated by dashed lines 64 for various elevations of the sun. FIGS.3A-3C illustrate how the angular orientation of the slatted panels20-24, or alternatively slatted panel 64 in FIG. 4, are tilted tomaintain direct ray of sunlight 64 at a 30° angle to the normal relativeto the front face of each slatted panel. The drawing in FIG. 3Aillustrates a very low elevation of the sun corresponding with earlymorning light entering an easterly facing window, or late afternoonsunlight entering a westerly facing window. On the other hand, thedrawing shown in FIG. 3C illustrates a relatively high elevation of thesun, as might correspond to the position of the summer sun near noontime entering a southernly-facing window.

Those skilled in the art will note that the slatted panels shown inFIGS. 3B and 3C are oriented in a near horizontal position and provideminimal interference with vision through the spaces between successiveslatted panels so that a person occupying the illuminated space may viewthe outdoors between the slatted panels. Only when sunlight strikes theshade mechanism at a low elevational angle (for vertical light openings)is vision through shade mechanism 16 somewhat curtailed, as shown inFIG. 3A. Thus, by designing the slatted panels to reject direct rays ofsunlight striking from an oblique angle relative to the front face ofthe slatted panels, outward vision through the spaces between adjacentslatted panels can be maximized.

It should also be recalled that one of the objectives of the presentinvention is to reflect away from the illuminated space direct rays ofsunlight while permitting the passage of indirect rays of sunlight. Inthis regard, the construction of the prismatic slatted panels will nowbe described in greater detail. As shown in FIG. 4, the front face ofslatted panel 64 is relatively smooth, while the rear face of slattedpanel 64 has, in cross section, a series of ridges formed by a series oflinear prisms. FIG. 5 is an enlarged cross section of slatted panel 64,wherein the front face thereof is designated by reference numeral 68,and wherein the rear face thereof is designated generally by referencenumber 70. Slatted panel 64 serves to reflect direct rays of sunlightthrough internal reflection of light rays within prisms formed upon rearface 70. While a variety of forms of such prisms may be used, FIG. 5illustrates one of the preferred forms wherein a series of 3-facedlinear prisms are formed across the width of rear face 70 of each suchslatted panel.

Referring to FIG. 5, one of such 3-faced linear prisms includes a firstface 72, a second face 74, and a third face 76. Preferred materials forconstructing such prismatic slatted panels include glass, acrylic,polycarbonate or other clear materials having an index of refractionsuitable for achieving internal reflection at a prismatic surface. Thelinear prisms shown in cross section in FIG. 5 extend for the fulllength of each slatted panel parallel to the longitudinal axis thereof,and accordingly, such slatted panels may be manufactured commerciallyusing extrusion, embossing, cutting, milling processes, injectionmolding processes, or compression molding processes.

Still referring to FIG. 5, it will be noted that first face 72 andsecond face 74 are of substantially equal width and are orientedperpendicular to one another so that an internal angle of substantially90° is formed therebetween. First face 72 and second face 74 have acommon longitudinal edge 78. Third face of the 3-faced linear prism isshown as extending between second face 74 and the first face 80 of thenext succeeding 3-faced linear prism. Third face 76 is typically of alesser width than first and second faces 72 and 74.

It will again be recalled that, in order to maximize vision through thespaces between adjacent slatted panels, it is desirable to maximizereflection of direct rays of sunlight striking front face 68 of panel 64at an angle of approximately 30° to the normal. Within FIG. 5, anincident ray of direct sunlight is designated by arrow 82. As shown inFIG. 5, incident ray 82 approaches from an angle of 30° relative to thenormal. As ray 82 passes into light-transmissive panel 64, the light rayis bent due to refraction and, assuming an index of refraction ofapproximately 1.5, the ray is redirected along the path shown by arrow84 at an angle of approximately 20° to the normal. In order to maximizeinternal reflection of refracted ray 84, second face 74 of the 3-facedlinear prism is set at an angle of 45° relative to refracted ray 84.Upon striking second face 74, refracted ray 84 is reflected along thepath shown by arrow 86, perpendicular to refracted ray 84. Because firstface 72 of the 3-faced linear prism is perpendicular to second face 74,reflected ray 86, upon striking first face 72, is again reflected alongthe path shown by arrow 88, perpendicular to reflected ray 86 andparallel to refracted ray 84. Upon striking front face 68, reflected ray88 is again refracted at the air interface along the path designated byarrow 90. Thus, refracted ray 90 is emitted at the same angle and in thesame general direction as incident ray 82.

Those skilled in the art will appreciate that a line bisecting the angleformed between first face 72 and second face 74 would extend parallel torefracted ray 84 and reflected ray 88, and hence would be oriented atapproximately a 20° angle relative to the normal. Because the linearprisms shown in FIG. 5 extend along the entire longitudinal axis ofslatted panel 64, one may imagine a plane which bisects the angle formedbetween faces 72 and 74, such plane lying at an angle of 20° to thenormal relative to front face 68. Third face 76 is preferably madeparallel to the imaginary plane bisecting the angle formed by faces 72and 74. Thus, third face 76 lies at an angle of approximately 20° to thenormal relative to front face 68. By orienting third face 76 in thismanner, maximum packing density of such 3-faced linear prisms isachieved, while simultaneously preventing third face 76 from interferingwith the internal reflection of direct rays of sunlight.

Due to the daily movements of the sun, the sun will not always bedirectly in front of the window in which the shade mechanism isinstalled; accordingly, direct rays of sunlight will often strike theslatted panels from one side or the other, at an angle other than 90° tothe longitudinal axis of each slatted panel. The tilt control mechanismdescribed above in regard to FIG. 1 is designed to maintain the slattedpanels in a rotational position such that a plane lying parallel to thelongitudinal axis of one of the slatted panels and containing a directray of sunlight intercepts the front face of the slatted panel at anangle of approximately 30° to the normal. While the incident ray ofdirect sunlight 82 shown in FIG. 5 has an angle of incidence of 30° tothe normal, it should be understood that the 3-faced linear prisms shownin FIG. 5 will also internally reflect rays of light deviating somewhatfrom 30° to the normal. The angle of 30° merely represents the centralfocal angle for such linear prisms; a predetermined band of angles oflight that are also internally reflected extends substantiallysymmetrically about the aforementioned central focal angle. For example,when direct rays of sunlight are oriented substantially perpendicular tothe longitudinal axes of the slatted panels, then the 3-faced linearprisms shown in FIG. 5 internally reflect rays of light which fallwithin the band of approximately 25°-35° to the normal relative to frontface 68 of the slatted panel. When the sun is to the side of the lightopening, and the rays of light are oriented other than perpendicular tothe longitudinal axes of the slatted panels, then the band of reflectedrays widens beyond the aforementioned 25°-35° angular range. Indirectrays of light striking front face 68 outside the aforementioned band ofangles, and which enter panel 64 are not reflected back out front face68 thereof, but are principally transmitted through rear face 70 intothe space to be illuminated. Thus the prisms formed upon the rear face70 of the slatted panels 64 are highly selective with respect to therays of light which are rejected from the space to be illuminated.

While FIG. 5 shows the central focal angle for internally reflected raysof sunlight to be at 30° to the normal relative to front face 68 of theslatted panel, it should be understood that the central focal angle neednot be precisely 30°. The prisms formed upon the rear face of theslatted panels may be formed so that the central focal angle lies withina range of about 20°-40° to the normal, relative to the front face ofthe slatted panel, while still permitting good overall visibilitybetween adjacent slats of the shade mechanism. Assuming that the centralfocal angle lies within the range of 20°-40° and an index of refractionof 1.5, then the plane bisecting the angle between faces 72 and 74 wouldlie at an angle in the range of approximately 13°-26° relative to thenormal. The prisms are preferably designed so that the central focalangle lies in the range of 25°-35° to the normal (corresponding with abisection angle in the range of 16°-23° to the normal), with 30° beingthe preferred value for vertical light openings in general.

Within FIGS. 4 and 5, slatted panels 64 are shown as being substantiallyflat and as having a substantially planar front face 68. Referring toFIG. 6, it will be appreciated that prismatic reflective panels may alsobe formed having a generally curved shape. It is sometimes desirable toimpart a cross-sectional, lateral curve to such slatted panels torigidify the same, particularly when the slatted panels extend over asignificant length. Referring to FIG. 6, it will be noted that a seriesof five 3-faced linear prisms are shown extending laterally acrossslatted panel 92, the five prisms being designated generally byreference numerals 93, 94, 95, 96 and 97; within FIG. 6, prism 93 isshown at the left most end of the drawing, while prism 97 is shown atthe right most end of the drawing. Imparting a curve to front face 98 ofpanel 92 somewhat complicates the design of linear prisms 93-97. Forexample, assuming that direct rays of sunlight strike front face 98 atan angle of approximately 30° to the normal near the central portionthereof overlying prism 95, incident rays of light striking front face98 proximate prism 93 will be at an angle of less than 30° to thenormal, while incident rays of light striking front face 98 near prism97 will approach from an angle greater than 30° relative to the normal.Accordingly, the refracted rays of direct sunlight passing into panel 92will be oriented in somewhat different directions, and consequently, theangular orientation of each linear prism must be individuallydetermined. Panel 92 shown in FIG. 6 has a front face 98 which extendsthrough an arc of curvature of approximately 29°. The angles shownwithin FIG. 6 indicate the manner in which the linear prisms areoriented from the left most end of the figure to the right most end ofthe figure. In each case, each linear prism includes first and secondfaces forming a 90° internal angle for internally reflecting direct raysof sunlight that strike front face 98 and are refracted within panel 92.

Prism 95 may be regarded as a central linear prism as it is locatedsubstantially near the center of the lateral cross section of panel 92.Accordingly, prism 95 is oriented so that its third face 95'" and aplane bisecting its first and second faces 95' and 95" are directed atan angle of approximately 20° to a line lying normal to the centralportion of front face 98. Remaining prisms 93, 94, 96, and 97 areoriented to internally reflect rays of sunlight incident from the sameelevational angle as rays of light incident upon the central portion ofpanel 92. In this manner, all of the prisms simultaneously internallyreflect direct rays of sunlight incident upon all portions of front face98.

It will be recalled that another objective the present invention is toevenly diffuse light transmitted by the slatted panels into the room orother space to be illuminated. Referring to FIG. 7A, a prismaticlight-transmissive slatted panel 100 is shown having a front face 102and a rear face designated generally by reference numeral 104. Adiffusion panel 106 is shown in FIG. 7A associated with prismatic panel100 and positioned adjacent rear face 104 thereof. For relatively flatprismatic panels, the associated diffusion panel extends substantiallyparallel thereto. In the case of arcuately curved prismatic panels, likethat shown in FIG. 7A, diffusion panel 106 extends through a generallysimilar arcuate curve and extends substantially parallel thereto at anygiven portion of prismatic panel 100. The purpose of diffusion panel 106is to evenly diffuse and disperse light emitted from rear face 104 ofprismatic panel 102. Accordingly, diffusion panel 106 may be made of atranslucent material to achieve such purpose. It should be rememberedthat the addition of diffusion panel 106 to prismatic panel 100 does notsignificantly impact the ability to see through a shade mechanismincorporating such prismatic panels when constructed according to theteachings of the present invention, because the shade mechanism isadapted to permit viewing through the spaces between adjacent slattedpanels, rather than through the slatted panels themselves.

As an alternative to the formation of diffusion panel 106 by using atranslucent material, transparent materials may also be used to formdiffusion panel 106 if an irregular surface is formed thereon. Methodsof forming such an irregular surface upon the diffusion panel materialinclude embossing or rolling the surface, as well as sand blasting thesurface to form a mat finish. Diffusion panel 106 can vary in color andtint, if desired, to impart a particular color to the light transmittedby the shade mechanism.

As shown in FIG. 7A, diffusion panel 106 may extend in a positionslightly spaced apart from, and out of contact with, rear face 104 ofpanel 100, whereby prismatic panel 100 and diffusion panel 106 define aninsulating dead air space. Forming the slats of the shade mechanism inthis manner can be used to form an insulating blanket at night by fullyclosing the slats to a near vertical position such that their edgesoverlap, thereby reducing heat loss or heat gain through the lightopening during the night.

Still referring to FIG. 7A, diffusion panel 106 includes a first edgeclip 108 extending from one side edge thereof, and a second edge clip110 extending from the opposing side edge thereof. Edge clip 108includes a finger 112 which extends over and around front face 102 ofprismatic panel 100. Similarly, edge clip 110 includes a finger 114which extends over and around the opposing side edge of front face 102.Edge clips 108 and 110 engage and rest against the opposing side wallsof prismatic panel 100, while fingers 112 and 114 maintain diffusionpanel 106 in the desired relationship with prismatic panel 102. FIGS.7B, 7C and 7D illustrate alternate methods of securing diffusion panel106 to prismatic panel 100. In FIG. 7B, side wall 116 extends upwardlyfrom the edge of diffusion panel 106 and is secured by a weld 118 to aside wall of prismatic panel 100. In FIG. 7C, diffusion panel 106includes upwardly extending side walls along the opposing longitudinaledges thereof, one of such sidewalls being shown by reference numeral118. Thus, diffusion panel 106 is in the form of a channel or trayadapted to receive prismatic panel 102, which is retained therein underthe force of gravity. In turn, interconnecting rung 33 of rope ladder 32provides support for diffusion panel 106.

In FIG. 7D, an edge bracket, like that designated by reference numeral120, is provided along each longitudinal edge of prismatic panel 100 anddiffusion panel 106. The side edges of prismatic panel 100 and diffusionpanel 106 are secured to edge bracket 120 by a suitable adhesive.

FIGS. 8A and 8B illustrate a manner in which a prismatic panel and itsassociated diffusion panel may be formed as a unitary hinged structure.Portion 122 is formed with a smooth front face and a prismatic rear faceto form a prismatic reflective panel, while portion 124 is initiallyformed as a clear transparent panel. Portions 122 and 124 are joined bya narrowed region 126 which extends longitudinally through the structureto hingedly connect portion 122 to portion 124. Following extrusion orinjection molding of the structure shown in FIG. 8A from a clear,light-transmissive material, one or both faces of portion 124 areprocessed, as by sandblasting, to form a light-diffusing mat finish. Asshown in FIG. 8B, the structure is then folded about its hinged joint126 to position prismatic panel portion 122 directly above diffusionportion 124. As shown in FIG. 8B, diffusion panel portion 124 is thenpositioned immediately below and adjacent to the prismatic surface ofprismatic panel 122.

FIG. 9 illustrates in cross section a flat prismatic panel usingthree-faced linear prisms, like those described above in regard to FIG.5, except that an extension member, shown in dashed outline andidentified by reference numeral 128, extends from the third face 130 ofat least one of the linear prisms. Extension member 128 includes acentral portion 132 which extends generally away from front face 134 ofthe prismatic panel. A pair of arms 136 and 138 extend from the remoteend of central portion 132 generally parallel to front face 134 foradding structural strength to the prismatic panel. Extension member 128may also serve as a support member to which an associated diffusionpanel may be attached. In FIG. 9, the diffusion panel 137 is shown asbeing secured to arms 136 and 138 of extension member 128.

Embodiments of the present invention which have been described abovehave each used prismatic reflective panels having a smooth front faceadapted to be directed toward the sun. It has been determined that aportion of the otherwise useable indirect rays of sunlight are reflectedoff of the front face of the prismatic panel rather than beingtransmitted through the prismatic panel. To minimize the loss of suchindirect rays of sunlight due to reflection off of the front face of theprismatic panels, the front face of such panels may be modified from asmooth surface to a stepped surface, as shown in FIG. 10. Prismaticpanel 140 shown in FIG. 10 has a stepped front face designated generallyby reference numeral 142 consisting of alternating first and secondsurfaces arranged perpendicular to one another. First surfaces 144 and146 are each disposed at an angle of approximately 30° from the frontface of slatted panel 140 as a whole, i.e., at an angle of approximately30° to the lateral axis of panel 140. Second surfaces 148 and 150 extendperpendicular to first surfaces 144 and 146 and serve to interconnectalternating first surfaces. An incident ray of sunlight is shown in FIG.10 by arrow 152, and, as noted in FIG. 10, ray 152 is not refracted asit enters first surface 146 because ray 152 is substantiallyperpendicular to surface 146. The rear face of prismatic panel 140 isdesignated generally by reference numeral 154 and includes a series of3-faced linear prisms formed thereupon. However, because direct rays ofsunlight are not refracted within panel 140, the linear prism formed byfaces 156 and 158 is oriented such that a plane bisecting the angleformed therebetween extends parallel to ray 152. Similarly, the thirdface 160 of the linear prism defined by faces 156 and 158 is alsopositioned parallel to ray 152, i.e., perpendicular to first surface146. As shown in FIG. 10, the number of steps formed upon front face 142may advantageously be made equal to the number of 3-faced linear prismsformed upon rear face 154 of panel 140.

Within the embodiments of the present invention described above, theprismatic panels used to reflect direct rays of sunlight haveincorporated linear prisms. However, those skilled in the art willappreciate that other types of prisms exhibiting internal reflection mayalso be formed upon the rear face of the prismatic panel in order toreflect direct rays of sunlight away from the space to be illuminated.With reference to FIG. 11A, multifaceted pyramidal prisms, such as prism162, are formed upon the rear face of prismatic panel 163. As shown inFIG. 11A, pyramidal prism 162 includes three triangular faces whichjointly terminate in an apex directed away from the rear face of panel163. Each pyramidal prism has a base which lies in common with otherpyramidal prisms formed upon the rear face of panel 163. FIGS. 11B, 11C,and 11D show examples of 4-sided, 5-sided, and 6-sided pyramidaltriangular prisms, respectively, which may also be used for internallyreflecting direct rays of sunlight entering the prismatic panel. Thoseskilled in the art will appreciate that the various faces of thetriangular pyramidal prisms may be oriented other than at symmetricalangles in order to reflect direct rays of sunlight striking the frontface of each prismatic panel at an oblique angle. FIG. 12A illustratesan example of a flat prismatic panel 166 used in combination with a flatdiffusion panel 168. However, as indicated in FIG. 12B, prismatic panelsmay also be formed as stepped or segmented structures. Prismatic panel170 shown in FIG. 12B includes a series of three segments 172, 174, and176. Each such segment preferably includes a front face directed at anangle of approximately 30° from the lateral axis of panel 170.Accordingly, direct rays of sunlight to be internally reflected by panel170 strike the front face of each such segment perpendicular thereto.The rear face of each such segment may consist of 2-faced linear prismsforming internal angles of 90° wherein each face extends at a 4520 anglerelative to the front face of each segment. Diffusion panel 178 extendsbehind prismatic panel 170 substantially parallel to the lateral axisthereof for diffusing indirect sunlight transmitted thereby.

FIG. 12C generally illustrates an alternate embodiment of the prismaticpanels and related diffusion panels wherein the prismatic panel 178 isbent into two halves 180 and 182 each having a smooth planar front faceand a rear prismatic face. An associated diffusion panel 184 is alsobent to provide a first half 186 lying parallel to prismatic portion180, and a second half 188 lying parallel to prismatic portion 182.

Another form of slatted panel is shown in FIG. 13. The slatted panelshown in FIG. 13 is designated generally by reference numeral 300 andincludes a smooth, relatively flat front face 302. The rear face ofslatted panel 300 includes a series of first surfaces, designated byreference numerals 304, 306, 308 and 310 each extending parallel to thelongitudinal axis of slatted panel 300 and each generally parallel toeach other. The rear face of slatted panel 300 also includes a series ofsecond surfaces 312, 314 and 316 each interposed between successivepairs of the aforementioned first surfaces. Thus, for example, secondsurface 312 is interposed between first surface 304 and second surface306. Preferably, second surface 312 extends generally perpendicular toboth first surface 304 and second surface 306.

Each first surface 304, 306, 308 and 310 of the rear face of slattedpanel 300 has formed thereupon at least one prismatic surface forinternally reflecting direct rays of sunlight, such as prism 318 onfirst surface 306. Preferably, each first surface 304, 306, 308 and 310has formed thereupon a plurality of 2-faced linear prisms which extendparallel to the longitudinal axis of the slatted panel for substantiallythe full length thereof. Each such linear prism includes a first face320 and a second face 322 of approximately equal width and having acommon longitudinal edge 324. Preferably, the internal angle formedbetween faces 320 and 322 is 90°.

As shown in FIG. 13, a plane, designated by dashed line 330, bisectingone of the 2-faced linear prisms intersects front face 302 at an angleof approximately 20° to the normal. As also shown in FIG. 13, secondsurface 314 also extends at an angle of 20° to the normal relative tofront face 302. Similarly, remaining second surfaces 312 and 316 extendparallel to second surface 314.

Within FIG. 13, incident direct ray of sunlight 332 is shown orientedalong the central focal angle of 30° to the normal relative to frontface 302. Incident ray 332 is refracted along the path designated 334,at an angle of approximately 20° to the normal, assuming an index ofrefraction of 1.5. Linear prism 318 internally reflects ray 334 anddirects it back toward front face 302 along the path designated 336. Asshown, reflected ray 336 extends at an angle of 20° to the normal.Reflected ray 336 exits from front face 302 as reflected ray 338 at anangle of 30° to the normal relative to front face 302. While incidentray 332 is shown being coincident with the central focal angle of 30°,it should be understood that each of the linear prisms also serves tointernally reflect rays of light within a predetermined band of incidentangles extending substantially symmerically about the central focalangle. Moreover, while the central focal angle shown in FIG. 13 is setat 30° to the normal, the central focal angle may vary within the rangeof 20°-40° to the normal, and still provide sufficient visibilitybetween adjacent slatted panels of the shade mechanism; the centralfocal angle is preferably oriented within the range of 25°-35° to thenormal.

Referring now to FIG. 14, a slatted panel 340 is shown having a rearface substantially similar to that shown in FIG. 13. However, the frontface of slatted panel 340 has a stepped surface including a series offirst surfaces 342, 344, 346, and 348. The stepped front face alsoincludes a series of second surfaces 350, 352, 354 and 356. Features ofthe rear face of slatted panel 340 common to those shown in FIG. 13 aredesignated by like reference numerals.

Within FIG. 14, second surface 352 is oriented at substantially 90° tofirst surfaces 342 and 344. Each of first surfaces 342, 344, 346 and 348extends substantially parallel to the longitudinal axis of slatted panel340 and parallel to one another. Similarly, second surfaces 350, 352,354 and 356 extend substantially parallel to the longitudinal axis ofslatted panel 340 and parallel to one another.

As shown in FIG. 14, first surfaces 342, 344, 346 and 348 are intendedto be directed toward incident direct rays of sunlight for permittingsuch direct rays to strike such first surfaces substantiallyperpendicular thereto. Thus, within FIG. 14, incident light ray 356 andreflected light ray 358 are shown extending perpendicular to firstsurface 344. Each of first surfaces 342, 344, 346 and 348 is oriented toextend at an angle of substantially 30° to the front face of slattedpanel 340 as a whole, as represented by dashed line 360. Similarly,first surfaces 304, 306, 308 and 310 of the rear face of slatted panel340 are oriented at substantially 30° to the front face of slatted panel340 as a whole. Second surfaces 312, 314 and 316 of the rear face ofslatted panel 340 each extend substantially perpendicular to firstsurfaces 342, 344, 346 and 348 of the front face of slatted panel 340.First surface 304 of the rear face of slatted panel 340 includes a2-faced linear prism 362 which may be bisected by a plane, (designatedby dashed line 364) which extends substantially perpendicular tooverlying first surface 342 of the front face thereof. As shown in FIG.14, the number of steps formed upon the front face of slatted panel 340may be equal in number to the number of steps formed upon the rear faceof slatted panel 340.

While the various embodiments of the present invention described hereinhave been illustrated with horizontally-mounted prismatic slattedpanels, those skilled in the art will also appreciate that prismaticpanels constructed in accordance herewith may also be suspendedvertically to form a vertical blind assembly adapted to reflect directrays of sunlight while admitting indirect rays of sunlight andmaximizing vision between adjacent slats. Such vertical blind assemblieswould probably be most useful for light openings facing in an easterlyor westerly direction. For light openings facing in a southernlydirection, the slats would necessarily need to be rotated through arelatively large angle during the course of each day in order tocontinuously reflect away direct rays of sunlight.

While the present invention has been described above in its preferredform as utilizing a solar tracking mechanism including a sun positionsensor and tilt drive motor, those skilled in the art will alsoappreciate thatthe prismatic panel tilt angle may also be manuallycontrolled if desired.

While the present invention has been described herein for use inconjunction with vertically oriented light openings, for examplewindows, it should also be appreciated that the shade mechanismdescribed herein may also be used in conjunction with horizontal orslanted light openings, for example, skylights.

Those skilled in the art will now appreciate that a shade mechanism hasbeen described which permits the passage of indirect rays of sunlightinto a space to be illuminated while reflecting away direct rays ofsunlight, simultaneously minimizing interference with vision through thespaces between the slatted panels of the shade mechanism. It will alsobe appreciated that such a shade mechanism may be used in conjunctionwith diffusion panels to more evenly diffuse the light transmitted bysuch prismatic panels without restricting vision between these slattedpanels. While the invention has been described with reference to severalpreferred embodiments thereof, the description is for illustrativepurposes only and is not to be construed as limiting the scope of theinvention. Various modifications and changes may be made by thoseskilled in the art without departing from the true spirit and scope ofthe invention.

I claim:
 1. A shade mechanism for permitting the passage of indirectrays of sunlight into a space to be illuminated while reflecting directrays of sunlight away from the space to be illuminated, said shademechanism being adapted to minimize interference with vision through theshade mechanism for a person located within the illuminated space, saidshade mechanism comprising in combination:(a) a plurality of slattedpanels extending parallel to one another and spaced apart from oneanother, each of said plurality of slatted panels extending about alongitudinal axis thereof; (b) support means for supporting saidplurality of slatted panels parallel to one another, said support meanssupporting each of said plurality of slatted panels for rotation aboutthe longitudinal axis thereof; (c) tilt means cooperating with saidsupport means for causing each of said plurality of slatted panels torotate in unison about its longitudinal axis while maintaining saidplurality of slatted panels parallel to one another; (d) each of saidplurality of slatted panels being composed of a substantially clear,light transmissive material, each such panel having a front face forbeing directed at the sun and an opposing rear face, said rear face ofeach such panel having prisms formed thereon, said prisms causing raysof sunlight that strike the front face of each such panel in apredetermined band of angles relative to the normal to be internallyreflected and emitted back out through the front face of each suchpanel, the predetermined band of angles extending substantiallysymmetrically about a central focal angle, said central focal angleextending within a range of about 20°-40° relative to the normal whilesaid prisms permitting rays of sunlight that strike the front face ofeach such panel from an angle that lies outside said predetermined bandof angles relative to the normal to be transmitted therethrough into thespace to the illuminated.
 2. A shade mechanism as recited by claim 1wherein said central focal angle extends within a range of about 25°-35°to the normal relative to the front face of each such panel.
 3. A shademechanism as recited by claim 2 wherein said central focal angle extendsat substantially 30° to the normal relative to the front face of eachsuch panel.
 4. A shade mechanism as recited by claim 1 wherein said tiltmeans is adapted to position said plurality of slatted panels in amanner such that a plane lying parallel to the longitudinal axis of oneof said slatted panels and containing a direct ray of sunlightintercepts the front face of said slatted panel at an angle ofapproximately 30° to the normal to maximize reflection of direct rays ofsunlight while minimizing interference with vision through the spacesbetween adjacent slatted panels.
 5. A shade mechanism as recited byclaim 4 wherein said tilt means includes solar tracking means forsensing the position of the sun and for rotating said plurality ofpanels in response to movements of the sun in order to maintain thefront face of each such panel such that a line normal thereto forms anangle of approximately 30° with said plane that lies parallel to thelongitudinal axis of said one slatted panel and that contains a directray of sunlight striking the front face of said one slatted panel.
 6. Ashade mechanism as recited by claim 1 including a plurality of diffusionpanels, each diffusion panel being associated with a corresponding oneof said slatted panels and being positioned adjacent the rear face ofeach such slatted panel substantially parallel thereto for diffusinglight transmitted through each such slatted panel to more evenlyilluminate the space to be illuminated.
 7. A shade mechanism as recitedby claim 6 wherein each of said plurality of diffusion panels is made ofa translucent material.
 8. A shade mechanism as recited by claim 6wherein each of said plurality of diffusion panels is made of atransparent material upon which an irregular surface is formed to causelight passing therethrough to be diffused.
 9. A shade mechanism asrecited by claim 6 wherein each of said plurality of diffusion panels issupported substantially out of contact with its corresponding slattedpanel to bound an insulating airspace therebetween to lessen the passageof heat through said shade mechanism when said plurality of slattedpanels are rotated to a closed position.
 10. A shade mechanism asrecited by claim 6 wherein each of said plurality of diffusion panelshas clips which extend from opposing side edges of each such diffusionpanel, said clips being adapted to extend over and around opposinglongitudinal edges of each slatted panel in order to maintain eachdiffusion panel in close proximity to the rear face of its correspondingslatted panel.
 11. A shade mechanism as recited by claim 6 wherein eachof said plurality of diffusion panels includes upwardly extending armsalong the opposing longitudinal edges thereof, and wherein said upwardlyextending arms are welded to the opposing longitudinal edges of acorresponding one of said plurality of slatted panels in order tomaintain each diffusion panel in close proximity to the rear face of itscorresponding slatted panel.
 12. A shade mechanism as recited by claim 6wherein each of said plurality of diffusion panels is in the form of atray into which a corresponding one of said plurality of slatted panelsis received, said support means supporting said plurality of diffusionpanels which, in turn, support said plurality of slatted panels.
 13. Ashade mechanism as recited by claim 6 wherein each of said plurality ofslatted panels and a corresponding one of said plurality of diffusionpanels form a unitary hinged structure, one longitudinal edge of saidslatted panel being hingedly connected to one longitudinal edge of saiddiffusion panel, said diffusion panel being folded under to underlie therear face of said slatted panel.
 14. A shade mechanism as recited byclaim 6 wherein said tilt means includes solar tracking means forsensing the position of the sun and for rotating said plurality ofslatted panels in response to movements of the sun.
 15. A shademechanism as recited by claim 14 wherein said tilt means maintains thefront face of each slatted panel in a reflective position such that aplane that lies parallel to the longitudinal axis of one such slattedpanel and containing a direct ray of sunlight that strikes such slattedpanel forms an angle of approximately 30° with a line normal to thefront face of such slatted panel to maximize reflection of direct raysof sunlight.
 16. A shade mechanism as recited by claim 14 wherein saidtilt means selectively maintains the front face of each slatted panel inan offset position such that a direct ray of sunlight that strikes onesuch slatted panel approaches from an angle relative to the normal lyingoutside said predetermined band of angles that are internally reflectedby said prisms, to permit direct rays of sunlight to pass through suchslatted panel and to be dispersed by the diffusion panel associatedtherewith.
 17. A shade mechanism as recited by claim 1 wherein saidprisms formed upon the rear face of each of said slatted panels aremultifaceted pyramidal prisms.
 18. A shade mechanism as recited by claim1 wherein each of said slatted panels is substantially planar.
 19. Ashade mechanism as recited by claim 1 wherein each of said slattedpanels is curved in lateral cross section.
 20. A shade mechanism asrecited by claim 1 wherein the front face of each of said plurality ofslatted panels has a stepped surface, said stepped surface consisting ofalternating first and second surfaces arranged at substantially 90° toone another, each of the first surfaces being disposed at an angle ofapproximately 30° from the front face of the slatted panel as a whole,the first surfaces being adapted to be perpendicular to direct rays ofsunlight reflected by the prisms formed upon the rear face of eachslatted panel.
 21. A shade mechanism for permitting the passage ofindirect rays of sunlight into a space to be illuminated whilereflecting direct rays of sunlight away from the space to beilluminated, said shade mechanism being adapted to minimize interferencewith vision through the shade mechanism for a person located within theilluminated space, said shade mechanism comprising in combination:(a) aplurality of slatted panels extending parallel to one another and spacedapart from one another, each of said plurality of slatted panelsextending about a longitudinal axis thereof; (b) support means forsupporting said plurality of slatted panels parallel to one another,said support means supporting each of said plurality of slatted panelsfor rotation about the longitudinal axis thereof; (c) tilt meanscooperating with said support means for causing each of said pluralityof slatted panels to rotate in unison about its longitudinal axis whilemaintaining said plurality of slatted panels parallel to one another;and (d) each of said plurality of slatted panels being composed of asubstantially clear, light transmissive material, each such panel havinga front face for being directed at the sun and an opposing rear face,said rear face of each such panel having a series of 3-faced linearprisms formed thereon and extending parallel to the longitudinal axis ofeach slatted panel, each 3-faced linear prism having a first face and asecond face of approximately equal width and having a commonlongitudinal edge and forming an internal angle of substantially 90°therebetween, each 3-faced linear prism further including a third faceextending between successive pairs of first and second faces, said thirdface lying substantially parallel to a plane which bisects the angleformed between said first and second faces, said first and second facesinternally reflecting direct rays of sunlight striking the front face ofeach such panel in a predetermined band of angles and causing saidinternally reflected rays to be emitted back out through the front faceof each such panel, the predetermined band of angles extendingsubstantially symmetrically about a central focal angle, said centralfocal angle extending within a range of about 20°-40° to the normalrelative to the front face of each such panel.
 22. A shade mechanism asrecited by claim 21 wherein said central focal angle extends within arange of about 25°-35° to the normal relative to the front face of eachsuch panel.
 23. A shade mechanism as recited by claim 22 wherein saidcentral focal angle extends at substantially 30° to the normal relativeto the front face of each such panel.
 24. A shade mechanism as recitedby claim 21 wherein both said third face and the plane bisecting theangle formed between said first and second faces extend at an angle ofapproximately 20° to the normal relative to the front face of each suchpanel.
 25. A shade mechanism as recited by claim 21 wherein both saidthird face and the plane bisecting the angle formed between said firstand second faces extend at an angle in the range of approximately13°-26° to the normal relative to the front face of each such panel. 26.A shade mechanism as recited by claim 25 wherein both said third faceand the plane bisecting the angle formed between said first and secondfaces extend at an angle in the range of approximately 16°-23° to thenormal relative to the front face of each such panel.
 27. A shademechanism as recited in claim 21 wherein each of said slatted panels ismounted horizontally.
 28. A shade mechanism as recited by claim 21wherein said tilt means is adapted to position said plurality of slattedpanels in a manner such that a plane lying parallel to the longitudinalaxis of one of said slatted panels and containing a direct ray ofsunlight intercepts the front face of said slatted panel at an angle ofapproximately 30° to the normal to maximize reflection of direct rays ofsunlight while minimizing interference with vision through the spacesbetween adjacent slatted panels.
 29. A shade mechanism as recited byclaim 28 wherein said tilt means includes solar tracking means forsensing the position of the sun and for rotating said plurality ofpanels in response to movements of the sun in order to maintain thefront face of each such panel such that a line normal thereto forms anangle of approximately 30° with said plane that lies parallel to thelongitudinal axis of said one slatted panel and that contains a directray of sunlight striking the front face of said one slatted panel.
 30. Ashade mechanism as recited by claim 21 wherein each of said plurality ofslatted panels is curved in lateral cross section, and wherein saidseries of three-faced linear prisms includes at least one central linearprism located substantially near the lateral center of each slattedpanel, said central linear prism being oriented such that both its thirdface and a plane bisecting the angle formed between its first and secondfaces extend at angle of approximately 20° to a line lying normal to thecenter portion of the front face of each slatted panel, and wherein theremainder of said series of 3-faced linear prisms are oriented tointernally reflect rays of sunlight incident from the same elvationalangle as rays of sunlight internally reflected by said central linearprism.
 31. A shade mechanism as recited by claim 21 wherein each of saidslatted panels includes an extension extending from the third face of atleast one of said 3-faced linear prisms, said extension being directedgenerally away from the front face of the slatted panel for addingstructural strength to the slatted panel.
 32. A shade mechanism asrecited by claim 31 including a plurality of diffusion panels, eachdiffusion panel being associated with a corresponding one of saidslatted panels and being positioned proximate to the rear face of eachsuch slatted panel substantially parallel thereto for diffusing lighttransmitted through each such slatted panel to more evenly illuminatethe space to be illuminated, each of said plurality of diffusion panelsbeing attached to said extension extending from the third face of one ofsaid 3-faced linear prisms formed upon the rear face of the slattedpanel associated with each such diffusion panel.
 33. A shade mechanismas recited by claim 21 including a plurality of diffusion panels, eachdiffusion panel being associated with a corresponding one of saidslatted panels and being positioned adjacent the rear face of each suchslatted panel substantially parallel thereto for diffusing lighttransmitted through each such slatted panel to more evenly illuminatethe space to be illuminated.
 34. A shade mechanism as recited by claim21 wherein the front face of each of said plurality of slatted panelshas a stepped surface, said stepped surface consisting of alternatingfirst and second surfaces arranged at substantially 90° to one another,each of the first surfaces being disposed at an angle of approximately30° from the front face of the slatted panel as a whole, the firstsurfaces being adapted to be perpendicular to rays of sunlightinternally reflected by the 3-faced linear prisms formed upon the rearface of each slatted panel.
 35. A shade mechanism as recited by claim 34wherein the number of steps formed upon the front face of each slattedpanel is substantially equal to the number of 3-faced linear prismsformed upon the rear face thereof.
 36. A shade mechanism for permittingthe passage of indirect rays of sunlight into a space to be illuminatedwhile reflecting direct rays of sunlight away from the space to beilluminated, said shade mechanism being adapted to minimize interferencewith vision through the shade mechanism for a person located within theilluminated space, said shade mechanism comprising in combination:(a) aplurality of slatted panels extending parallel to one another and spacedapart from one another, each of said plurality of slatted panelsextending about a longitudinal axis thereof; (b) support means forsupporting said plurality of slatted panels parallel to one another,said support means supporting each of said plurality of slatted panelsfor rotation about the longitudinal axis thereof; (c) tilt meanscooperating with said support means for causing each of said pluralityof slatted panels to rotate in unison about its longitudinal axis whilemaintaining said plurality of slatted panels parallel to one another;(d) each of said plurality of slatted panels being composed of asubstantially clear, light transmissive material, each such panel havinga front face for being directed at the sun and an opposing rear face,said rear face of each such slatted panel having prisms formed thereonfor causing direct rays of sunlight that strike the front face of eachsuch panel within a predetermined range of angles to be internallyreflected and emitted back out through the front face of each suchpanel, while permitting rays of sunlight outside of said predeterminedrange to be transmitted therethrough into the space to be illuminated;and (e) a plurality of diffusion panels, each diffusion panel beingassociated with a corresponding one of said slatted panels and beingpositioned adjacent the rear face of each such slatted panelsubstantially parallel thereto for diffusing light transmitted througheach such slatted panel to more evenly illuminate the space to beilluminated.
 37. A shade mechanism as recited by claim 36 wherein eachof said plurality of diffusion panels is made of a translucent material.38. A shade mechanism as recited by claim 36 wherein each of saidplurality of diffusion panels is made of a transparent material uponwhich an irregular surface is formed to cause light passing therethroughto be diffused.
 39. A shade mechanism as recited by claim 36 whereineach of said plurality of diffusion panels is supported substantiallyout of contact with its corresponding slatted panel to bound aninsulating airspace therebetween to lessen the passage of heat throughsaid shade mechanism when said plurality of slatted panels are rotatedto a closed position.
 40. A shade mechanism as recited by claim 36wherein each of said plurality of diffusion panels has clips whichextend from opposing side edges of each such diffusion panel, said clipsbeing adapted to extend over and around opposing longitudinal edges ofeach slatted panel in order to maintain each diffusion panel in closeproximity to the rear face of its corresponding slatted panel.
 41. Ashade mechanism as recited by claim 36 wherein each of said plurality ofdiffusion panels includes upwardly extending arms along the opposinglongitudinal edges thereof, and wherein said upwardly extending arms arewelded to the opposing longitudinal edges of a corresponding one of saidplurality of slatted panels in order to maintain each diffusion panel inclose proximity to the rear face of its corresponding slatted panel. 42.A shade mechanism as recited by claim 36 wherein each of said pluralityof diffusion panels is in the form of a tray into which a correspondingone of said plurality of slatted panels is received, said support meanssupporting said plurality of diffusion panels which, in turn, supportsaid plurality of slatted panels.
 43. A shade mechanism as recited byclaim 36 wherein each of said plurality of slatted panels and acorresponding one of said plurality of diffusion panels form a unitaryhinged structure, one longitudinal edge of said slatted panel beinghingedly connected to one longitudinal edge of said diffusion panel,said diffusion panel being folded under to underlie the rear face ofsaid slatted panel.
 44. A shade mechanism as recited by claim 36 whereinsaid plurality of diffusion panels are tinted to impart colorization tothe light transmitted by said shade mechanism.
 45. A shade mechanism asrecited by claim 36 wherein said tilt means includes solar trackingmeans for sensing the position of the sun and for rotating saidplurality of slatted panels in response to movements of the sun.
 46. Ashade mechanism as recited by claim 45 wherein said tilt means maintainsthe front face of each slatted panel in a reflective position such thata plane that lies parallel to the longitudinal axis of one such slattedpanel and containing a direct ray of sunlight that strikes such slattedpanel forms an angle of approximately 30° with a line normal to thefront face of such slatted panel to maximize reflection of direct raysof sunlight.
 47. A shade mechanism as recited by claim 45 wherein saidtilt means selectively maintains the front face of each slatted panel inan offset position such that a plane that lies parallel to thelongitudinal axis of one such slatted panel and containing a direct rayof sunlight that strikes such slatted panel forms an angle of less than21° with a line normal to the front face of such slatted panel to permitdirect rays of sunlight to pass through such slatted panel and to bedispersed by the diffusion panel associated therewith.
 48. A shademechanism for permitting the passage of indirect rays of sunlight into aspace to be illuminated while reflecting direct rays of sunlight awayfrom the space to be illuminated, said shade mechanism being adapted tominimize interference with vision through the shade mechanism for aperson located within the illuminated space, said shade mechanismcomprising in combination:(a) a plurality of slatted panels extendingparallel to one another and spaced apart from one another, each of saidplurality of slatted panels extending about a longitudinal axis thereof;(b) support means for supporting said plurality of slatted panelsparallel to one another, said support means supporting each of saidplurality of slatted panels for rotation about the longitudinal axisthereof; (c) tilt means cooperating with said support means for causingeach of said plurality of slatted panels to rotate in unison about itslongitudinal axis while maintaining said plurality of slatted panelsparallel to one another; and (d) each of said plurality of slattedpanels being composed of a substantially clear, light transmissivematerial, each such panel having a front face for being directed at thesun and an opposing rear face, said rear face including a plurality offirst surfaces each extending parallel to the longitudinal axis of suchslatted panel, said rear face further including a plurality of secondsurfaces each interposed between successive pairs of first surfaces,each first surface having formed thereupon at least one 2-faced linearprism extending parallel to the longitudinal axis of such slatted panel,each 2-faced linear prism having a first face and a second face ofapproximately equal width and having a common longitudinal edge andforming an internal angle of substantially 90° therebetween, saidplurality of second surfaces each lying substantially parallel to aplane which bisects the angle formed between said first and secondfaces, said first and second faces internally reflecting direct rays ofsunlight striking the front face of each such slatted panel in apredetermined band of angles and causing said internally reflected raysto be emitted back out through the front face of each such slattedpanel.
 49. A shade mechanism as recited by claim 48 wherein thepredetermined band of angles extends substantially symmetrically about acentral focal angle, said central focal angle extending within a rangeof about 20°-40° to the normal relative to the front face of each suchpanel.
 50. A shade mechanism as recited by claim 49 wherein said centralfocal angle extends within a range of about 25°-35° to the normalrelative to the front face of each such panel.
 51. A shade mechanism asrecited by claim 50 wherein said central focal angle extends atsubstantially 30° to the normal relative to the front face of each suchpanel.
 52. A shade mechanism as recited by claim 51 wherein the theplane bisecting the angle formed between the first and second faces ofeach 2-faced linear prism is substantially at 20° to the normal relativeto the front face of each such slatted panel.
 53. A shade mechanism asrecited by claim 48 wherein the front face of each of said plurality ofslatted panels has a stepped surface, said stepped surface consisting ofalternating first and second surfaces arranged at substantially 90° toone another, each of the first surfaces of said front face beingdisposed at an angle of approximately 30° from the front face of theslatted panel as a whole, the first surfaces being adapted to beperpendicular to rays of sunlight internally reflected by the 2-facedlinear prisms formed upon the rear face of each slatted panel, the planebisecting the angle formed between the first and second faces of said2-faced linear prisms lying substantially perpendicular to an overlyingfirst surface of said front face.
 54. A shade mechanism as recited byclaim 53 wherein the number of first surfaces formed upon the front faceof each slatted panel is substantially equal to the number of firstsurfaces formed upon the rear face thereof.